Customer Guidance for WannaCrypt attacks

Today many of our customers around the world and the critical systems they depend on were victims of malicious “WannaCrypt” software. Seeing businesses and individuals affected by cyberattacks, such as the ones reported today, was painful. Microsoft worked throughout the day to ensure we understood the attack and were taking all possible actions to protect our customers. This blog spells out the steps every individual and business should take to stay protected. Additionally, we are taking the highly unusual step of providing a security update for all customers to protect Windows platforms that are in custom support only, including Windows XP, Windows 8, and Windows Server 2003. Customers running Windows 10 were not targeted by the attack today.

Details are below.

In March, we released a security update which addresses the vulnerability that these attacks are exploiting. Those who have Windows Update enabled are protected against attacks on this vulnerability. For those organizations who have not yet applied the security update, we suggest you immediately deploy Microsoft Security Bulletin MS17-010.

For customers using Windows Defender, we released an update earlier today which detects this threat as Ransom:Win32/WannaCrypt. As an additional “defense-in-depth” measure, keep up-to-date anti-malware software installed on your machines. Customers running anti-malware software from any number of security companies can confirm with their provider, that they are protected.

This attack type may evolve over time, so any additional defense-in-depth strategies will provide additional protections. (For example, to further protect against SMBv1 attacks, customers should consider blocking legacy protocols on their networks).

We also know that some of our customers are running versions of Windows that no longer receive mainstream support. That means those customers will not have received the above mentioned Security Update released in March. Given the potential impact to customers and their businesses, we made the decision to make the Security Update for platforms in custom support only, Windows XP, Windows 8, and Windows Server 2003, broadly available for download (see links below).

Customers who are running supported versions of the operating system (Windows Vista, Windows Server 2008, Windows 7, Windows Server 2008 R2, Windows 8.1, Windows Server 2012, Windows 10, Windows Server 2012 R2, Windows Server 2016) will have received the security update MS17-010 in March. If customers have automatic updates enabled or have installed the update, they are protected. For other customers, we encourage them to install the update as soon as possible.

This decision was made based on an assessment of this situation, with the principle of protecting our customer ecosystem overall, firmly in mind.

Some of the observed attacks use common phishing tactics including malicious attachments. Customers should use vigilance when opening documents from untrusted or unknown sources. For Office 365 customers we are continually monitoring and updating to protect against these kinds of threats including Ransom:Win32/WannaCrypt. More information on the malware itself is available from the Microsoft Malware Protection Center on the Windows Security blog. For those new to the Microsoft Malware Protection Center, this is a technical discussion focused on providing the IT Security Professional with information to help further protect systems.

We are working with customers to provide additional assistance as this situation evolves, and will update this blog with details as appropriate.

Update 5/22/2017: Today, we released an update to the Microsoft Malicious Software Removal Tool (MSRT) to detect and remove WannaCrypt malware. For customers that run Windows Update, the tool will detect and remove WannaCrypt and other prevalent malware infections. Customers can also manually download and run the tool by following the guidance here. The MSRT tool runs on all supported Windows machines where automatic updates are enabled, including those that aren't running other Microsoft security products.